Results 1 to 10 of 10
  1. #1
    mtbr member
    Reputation:
    Join Date
    May 2009
    Posts
    127

    Forerunner Elevation Tracking

    I'm thinking about buying either a Garmin Forerunner 305 or an Edge 305. The big difference for me is that according to Garmin the Edge has a barometric altimeter and the Forerunner does not. I was riding with someone last week that had the Forerunner and the data he emailed me included elevation data.

    Now I'm confused, does anyone know if the Forerunner does track elevation, and if so does it use a different means (satellite triangulation???)

    Any help is appreciated.

  2. #2
    Rep Power: Infinity
    Reputation: NateHawk's Avatar
    Join Date
    Dec 2003
    Posts
    12,698
    There are many different Forerunners. It's probable that there are some with and some without the barometric altimeter, but Garmin's compare utility on their website will show you what features are included with each receiver. That link only shows 4 receivers, but it gives you an idea what's going on.

  3. #3
    Disgruntled Peccary
    Reputation: dysfunction's Avatar
    Join Date
    Aug 2009
    Posts
    867
    The forerunner 305's elevation data is notoriously bad, but it does track it and many 3rd party software packages filter out the noise that causes the elevation discrepancies. If elevation data is crucial for you, I'd look more at an edge. For what it's worth, I'm unaware that any of the forerunners use a barometric pressure altimeter. I know my 405 doesn't and I don't believe the 405cx or 310 do either.
    mike

  4. #4
    mtbr member
    Reputation:
    Join Date
    Jan 2009
    Posts
    326
    Just to affirm the above posts.. none of the Forerunners have a barometric altimeter it seems.

    The Forerunners do use satellite data for elevation. The accuracy isn't bad in absolute terms and is sufficient to use for navigation in my experience, by comparing gps elevation to the contour lines on a topo map. But the +/- inaccuracy of 5m of the GPS (under good conditions, and it's often worse) seems to lead to overestimates of total climbing and descending elevation changes over the course of a ride. At least that is my experience..

    You can easily 'correct' the Forerunners elevation data using online digital elevation data. SportTracks is one of the software packages that makes this as simple as pressing a button. BUT, the correction is only as good as the digital elevation data that is available. For most regions that data is pretty coarse.

  5. #5
    mtbr member
    Reputation:
    Join Date
    May 2009
    Posts
    127
    Thanks for the answers. For the $100 price difference I'll probably just go with the Forerunner since I don't require exact elevation data.

  6. #6
    mtbr member
    Reputation: MikeDee's Avatar
    Join Date
    Nov 2004
    Posts
    1,106
    I have an Avocet 50 altimeter computer and a Forerunner 305. The Forerunner typically shows twice the amount of feet climbed than the Avocet. The Avocet is much more accurate.

  7. #7
    Disgruntled Peccary
    Reputation: dysfunction's Avatar
    Join Date
    Aug 2009
    Posts
    867
    Oh yea, it's even funnier when you make the same ride twice. Same exact loop...




    btw, this is on the 405.
    mike

  8. #8
    nuf
    nuf is offline
    mtbr member
    Reputation:
    Join Date
    Sep 2004
    Posts
    57
    I really thought the GPS elivation was a lot better.....hmmmmm....

  9. #9
    mtbr member
    Reputation: MikeDee's Avatar
    Join Date
    Nov 2004
    Posts
    1,106
    Quote Originally Posted by nuf
    I really thought the GPS elevation was a lot better.....hmmmmm....
    Yeah, this is one of those myths that will never die. My bike club had a climbing contest for a month of the year. Of course I used my Forerunner data. Most people simply believe that if it's GPS, it has to be accurate.

  10. #10
    Rep Power: Infinity
    Reputation: NateHawk's Avatar
    Join Date
    Dec 2003
    Posts
    12,698
    Quote Originally Posted by MikeDee
    Yeah, this is one of those myths that will never die. My bike club had a climbing contest for a month of the year. Of course I used my Forerunner data. Most people simply believe that if it's GPS, it has to be accurate.
    Yep, that myth needs to die. That topic is addressed in the sticky at the top of the page now, too. GPS elevation depends on having adequate satellite reception, and in order to calculate elevation, the GPS needs a lock on more satellites than for a simple position fix. So you can get a position fix, but with no elevation reading with the GPS altimeter.

    No way of calculating elevation is perfect. The earth is round and hilly. The only thing we know for certain is sea level, though that changes, too. The best method is to use barometric pressure since it doesn't require a complex mathematical model of the earth (which is error-prone since the earth is not a perfect sphere, anyway), except a barometric altimeter needs calibrating and corrections to account for weather changes during the activity. Now, the method of calibrating/correcting can introduce error, or at least fail to fully account for it, but that's another issue.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •